efficacy of a pacemaker algorithm in promotion of the intrinsic heart activity.

Conditions: Bradycardia; Sick Sinus Syndrome, AV Block

Summary: the purpose of this study is to provide evidence that the refined ventricular pacing algorithm leads to clinically relevant reduction (at least 50% reduction) of the incidence of ventricular pacing.

electrical stimulation in the apex of the right ventricle ( ventricular pacing) usually improves the heart function of patients with a pacemaker and can even be life-saving. however, evidence is accumulating that ventricular pacing may also have undesired long-term cardiac effects. therefore, it makes sense to limit ventricular pacing to the absolute required minimum. the functionality rvp (refined ventricular pacing) in the c-series 2nd generation pacemakers of vitatron b.v. arnhem, the netherlands is designed to reduce ventricular pacing. after implantation of the vitatron c50 d model c50a2 (pacemaker) or vitatron c60 dr model c60a2 (pacemaker) and a 4-6 weeks stabilization period, proper functioning of pacemaker and leads (stimulation- and sensing parameters) is checked. the pacemakers will be programmed according to predefined settings. in the following 4-weeks baseline period diagnostic data (atrial fibrillation burden and percentage of ventricular pacing (% vp)) are collected in the pacemaker memory. based on these data, patients will be excluded from further participation (patients with more than 15% atrial fibrillation) or subdivided into three groups: (a) \ 30% vp, sick sinus syndrome and normal conductivity (sss group), (c) \>30% vp, 1st or 2nd degree av block. patients in these three groups will be treated for 4 weeks alternatively with the rvp functionality switched on or off. the order will be determined by randomization. at the end of these two cross-over periods the % vp and the judgment of the patients of the last period will be assessed. adverse events will be recorded from the moment of study enrolment.

Eligibility criteria:
inclusion criteria: * patients shall be willing to sign the patient informed consent for this study * patients shall have at least one of the following indications for a pacemaker: - sick sinus syndrome with normal qrs complexes * first degree av block with a pr interval \<_220 ms for patients \<_ 70 years of age, or \<_ 260 for patients over 70 years * second-degree av block, mobitz i (wenckebach) or mobitz ii * patients shall be available for follow-up for the duration of their participation. exclusion criteria: * patients involved in another investigation study conducted in parallel to this study * patients younger than 18 years of age and/or patients that do not meet other local requirements for participation * pregnant patients * patients with lead integrity problems (and the lead is not being replaced) * patients with persistant af * patients with a complete av block * patients with nyha (new york heart association0 class iii and iv * patients who underwent thoracic surgery in the last three months or are expected to have in the near future * patients with a 2:1 block * patients with a life expectancy less than half a year

Keywords: refined ventricular pacing